1. Field of The Invention
The invention relates to a low insertion force (LIF) socket connector for connecting an electrical pin grid array (PGA) component to a circuit board and will have application to a assembling method of such socket.
2. The Prior Art
High pin count PGA components become popular in application of computer industry because of the requirements of high speed signal transmission and great processing capacity. It can be understood that the more the pins are, the higher the insertion force is when such PGA component is mated with the corresponding socket connector. Accordingly, to achieve low insertion force (LIF) or zero insertion force (ZIF) design in such PGA socket connector is desired. Many zero insertion force PGA sockets are developed as disclosed in U.S. Pat. Nos. 4,468,072, 4,498,725, 4,648,669, 4,674,811, 4,836,798, 4,887,974, 4,889,499, 4,988,310, 5,002,499, 5,013,256, 5,017,152, 5,037,321, 5,057,031, 5,059,135, 5,092,789, 5,123,855, 5,167,515, 5,186,642, 5,192,221 and 5,213,531. Such mechanically actuated ZIF socket employs a free-moving cam. In the open position, the cam allows the PGA component to be inserted and withdrawn without force. However, when the cam is actuated into the closed position via lever, hex nut etc., the normally closed contacts maintain a constant pressure on the PGA pins.
By contrast, the non-mechanically actuated LIF socket is mated to the socket with an applied force. Even though ZIF style is superior to LIF style from a viewpoint of technical consideration of insertion force, the former can not completely replace the latter in computer industry due to the fact that ZIF sockets are more than double the price of LIF sockets now because there are additional components thereof such as cams, levers, in ZIF sockets in comparison with LIF sockets. Therefore, some computer manufacturers still prefer to use LIF sockets in their product for consideration of the competitive price.
Contacts used in LIF PGA sockets are generally of two types. The first type is of two pieces design including a screw-machined cylindrical sleeve accompanying an inserted clip as disclosed in U.S. Pat. Nos. 4,186,990, 4,296,993, 4,470,649, 4,534,603, 4,728,304, 4,784,622, 4,981,450 and 5,232,382. The second type is of a one-piece stamped and formed design as disclosed in U.S. Pat. Nos. 3,602,875, 4,480,888, 4,707,052, 4,726,739, 4,934,967, 5,046,972 and 5,232,382. Because the one-piece stamped and formed contact is easier to manufacture and less expensive than the two-piece design, the former is generally intended to be used in computer industry.
While the disadvantages in conventional LIF PGA socket and its associated one-piece stamped and formed contacts as shown in the aforementioned U.S. Patents include that a large insertion force is required if the contact retention force is designedly high for assuring secure retention between the PGA pins and the socket contacts. Secondly, in manufacturing such socket, when the contact is assembled with the socket by insertion into the corresponding cavity in the socket, there is no auxiliary means to guide the movement of the contact along the cavity, so that the contact may be not in its position. As a result, the tilted contact may result in a larger insertion force for the inserted pin of the PGA component because of misalignment therebetween. Otherwise, the manufacturing tolerance is severely required much smaller for avoiding such assembling misalignment. Either of these two results is not desired by the connector manufacturer. Accordingly, the present invention is to provide a modified LIF PGA socket and contacts therein.